Field of the Invention
THE PRESENT INVENTION relates to a seat belt buckle and more particularly the invention relates to a seat belt buckle of the type intended for use in a motor vehicle. A typical buckle of this type receives a tongue which is mounted on the seat belt.
It has been found, with various buckles, in motor vehicles, that under certain circumstances the buckle may be subjected to an extremely high G force axially of the buckle, thus tending to move some of the components within the buckle against any spring force retaining the components in place. This high G force may be created if the buckle is rotated about an axis which is spaced from the buckle. Thus, under such circumstances the tongue may become released from the buckle, which is clearly undesirable. Various proposals have been made to overcome this defect, but certain of the proposals have been such that if the buckle is subjected to a rotation about a vertical axis passing through the buckle, this can lead to an inadvertent release of the tongue from the buckle.
It occasionally happens that when a motor vehicle is involved in an accident, a passenger, retained in the vehicle by the seat belt is in such a position that the seat belt is under tension. For example the vehicle may be upside down, and the person retained by the seat belt may eventually be suspended by the seat belt. In such a situation the tongue inserted into the buckle of the seat belt arrangement is subjected to a large force tending to withdraw the tongue from the buckle. The tongue is engaged by a locking member within the buckle, and if the design of the locking member is such that the locking member is drawn further towards the locking position by the force applied to the locking member from the tongue, then it may be difficult to release the seat belt from its buckle, and it will then be necessary to cut the seat belt to release the trapped person from the motor vehicle.